Described herein are toners, and developers containing the toners, preferably emulsion aggregation toners, having improved sensitivity to relative humidity through inclusion of silicate clay particles, preferably aluminosilicate particles, in the toner particles.
Emulsion aggregation toners are excellent toners to use in forming print and/or xerographic images in that the toners can be made to have uniform sizes and in that the toners are environmentally friendly. U.S. patents describing emulsion aggregation toners include, for example, U.S. Pat. Nos. 5,370,963, 5,418,108, 5,290,654, 5,278,020, 5,308,734, 5,344,738, 5,403,693, 5,364,729, 5,346,797, 5,348,832, 5,405,728, 5,366,841, 5,496,676, 5,527,658, 5,585,215, 5,650,255, 5,650,256, 5,501,935, 5,723,253, 5,744,520, 5,763,133, 5,766,818, 5,747,215, 5,827,633, 5,853,944, 5,804,349, 5,840,462, and 5,869,215, each incorporated herein by reference in its entirety.
One main type of emulsion aggregation toner includes emulsion aggregation toners that are acrylate based, e.g., styrene acrylate toner particles. See, for example, U.S. Pat. No. 6,120,967, incorporated herein by reference in its entirety, as one example.
Emulsion aggregation techniques typically involve the formation of an emulsion latex of the resin particles, which particles have a small size of from, for example, about 5 to about 500 nanometers in diameter, by heating the resin, optionally with solvent if needed, in water, or by making a latex in water using emulsion polymerization. A colorant dispersion, for example of a pigment dispersed in water, optionally also with additional resin, is separately formed. The colorant dispersion is added to the emulsion latex mixture, and an aggregating agent or complexing agent is then added to form aggregated toner particles. The aggregated toner particles are optionally heated to enable coalescence/fusing, thereby achieving aggregated, fused toner particles.
U.S. Pat. No. 5,462,828 describes a toner composition that includes a styrene/n-butyl acrylate copolymer resin having a number average molecular weight of less than about 5,000, a weight average molecular weight of from about 10,000 to about 40,000 and a molecular weight distribution of greater than 6 that provides excellent gloss and high fix properties at a low fusing temperature.
A continuing issue with acrylate-based emulsion aggregation toners is that such toners typically incorporate a functional group, for example an acrylic acid, to stabilize the particles in the aqueous phase, thereby allowing the particles to be formed. The inclusion of such functional groups may result in the toner particles having a higher low relative humidity (RH) zone charge (low RH zone as used herein refers to a RH condition of 15% at a temperature of about 10° C.) than desired. While efforts to combat this effect have included increasing the externally additive coverage upon the external surface of the toner particles, such can have negative effects such as increased production costs, the need for increased minimum fusing temperatures, etc.